1-Wire Humidity sensor + I/O-module

Around a PIC16F628 microcontroller a circuit is made to connect a SHT-11
( two wire Humidity sensor of Sensirion ) on a 1-wire ( © Dallas semiconductor ) network.

Besides the Humidity connection there are 13 I/O pins for general I/O and a 32 bits counter available.

Figure 1 Block schematic

Features

13** TTL-In/Outputs capable to drive 25mA
Connection of a SHT11 Humidity/Temperature Sensor ( see: http://www.sensirion.com/ )
32 bits counter (resetable) input ( one of the 13 inputs )
1-Wire input, 64 bits id, multidrop
4 x 32 bytes Eeprom to store user-info
Simple low cost 'one-IC' design
Low power: 3mA with no I/O port current, 4mA while converting.
Internal 'watchdog circuit', watching for a running processor

** When a SHT11 sensor is used, 11 I/O pins are free

See for the schematic: schematic.gif.

Information in PDF format: 1-WireIOPort.pdf

HEX-file for a PIC16F628: HexFile ( after download rename the file to .hex )

Figure 2 Prototype of the 1-Wire SHT11 humidity sensor / IO port

The unit is controlled by the 1-Wire protocol of Dallas semiconductor.
Some basic commands are build in the PIC16F628.

Build in commands

ROM-functions:

Read ROM	0x33
Match ROM	0x55
Skip ROM	0xCC
Search ROM	0x0F

Memory / Control commands

Command	Value	Description
Write Scratchpad	0x4E	Till 32 bytes can be written to the internal scratch memory
Read Scratchpad	0xBE	Till 32 bytes can be read from the internal scratchpad ( no CRC )
Copy Scratchpad	0x48	32 bytes are written to the Eeprom ( takes till 50mS ) ( 4 pages )
Recall EEprom	0xB8	32 bytes from Eeprom are copied into the scratchpad ( 4 pages )

Convert Sensor	0x44	Starts a conversion of the SHT11 sensor ( Takes apr. 300mS )
Read Sensor	0x45	Reads the SHT11 conversion results ( 10 bytes )

Reset Counter	0x01	Resets the 32 bits counter to zero
Read Counter	0x02	Reads the 32 bits counter ( message of 6 bytes ). Counter-input is PortA_4
Read IO-identification	0x03	Read the IO-module identification

Setup PortA	0xF3	Sets the Port A pins to be Input or Output
Setup PortB	0xF4	Sets the Port B pins to be Input or Output

Read PortA	0xF5	Reads the contents of PortA ( inputs PortA_0..PortA_4), 6 bits
Read PortB	0xF6	Reads the contents of PortB ( inputs PortB_1..PortB_7), 7 bits

Write PortA	0xF7	Writes the value to PortA, 6 bits
Write PortB	0xF8	Writes the value to PortB, 7 bits

On request a complete description of the commands can be send.

Applications

Humidity and temperature measurement with one circuit
Extend the number of I/O pins in your ( TINI ) 1-Wire network / circuit
Counter input for windspeed / raingauge
1-Wire printerport
LCD connection